<template>
  <div class="pagination">
    <button :disabled="pageNo <= 1" @click="$emit('changePageNo', pageNo - 1)">
      上一页
    </button>
    <button
      v-show="startEndPages.startPage > 1"
      @click="$emit('changePageNo', 1)"
    >
      1
    </button>

    <button v-show="startEndPages.startPage > 2">···</button>

    <button
      v-for="item in startEndPagesArr"
      :key="item"
      @click="$emit('changePageNo', item)"
      :class="item === pageNo ? 'active' : ''"
    >
      {{ item }}
    </button>

    <button v-show="startEndPages.endPage < totalPages - 1">···</button>
    <button
      v-show="startEndPages.endPage < totalPages"
      @click="$emit('changePageNo', totalPages)"
    >
      {{ totalPages }}
    </button>
    <button
      :disabled="pageNo >= totalPages"
      @click="$emit('changePageNo', pageNo + 1)"
    >
      下一页
    </button>

    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>
  
  <script>
export default {
  name: "Pagination",
  props: ["pageNo", "continuePages", "totalPages", "total"],
  methods: {},
  computed: {
    startEndPages() {
      const { pageNo, continuePages, totalPages } = this;
      let startPage = null;
      let endPage = null;
      if (continuePages > totalPages) {
        startPage = 1;
        endPage = totalPages;
      } else {
        startPage = pageNo - (continuePages - 1) / 2;
        endPage = pageNo + (continuePages - 1) / 2;
        if (pageNo <= 1) {
          startPage = 1;
          endPage = continuePages;
        }
        if (pageNo >= totalPages) {
          endPage = totalPages;
          startPage = totalPages - continuePages + 1;
        }
      }

      return { startPage, endPage };
    },

    // 计算出 遍历连续页，防止v-for和v-if一块使用
    startEndPagesArr() {
      const { startPage, endPage } = this.startEndPages;
      let arr = [];
      for (let i = startPage; i <= endPage; i++) {
        arr.push(i);
      }
      return arr;
    },
  },
};
</script>
  
  <style lang="less" scoped>
.pagination {
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>